Solid-state lighting devices (SSLDs) use semiconductor light-emitting diodes (LEDs), polymer light-emitting diodes (PLEDs), and organic light-emitting diodes (OLEDs) as sources of illumination. Generally, SSLDs generate less heat, provide greater resistance to shock and vibration, and have longer life spans than conventional lighting devices (e.g., florescent tubes, light bulbs) that use filaments, plasma, or gas as sources of illumination.
A conventional type of SSLD is a “white light” LED. White light requires a mixture of wavelengths to be perceived by human eyes. However, LEDs typically only emit light at one particular wavelength (e.g., blue light), so LEDs must be modified to emulate white light. One conventional technique for doing so includes depositing a converter material (e.g., phosphor) on the LED. For example, as shown in FIG. 1A, a conventional LED device 10 includes a support 2 carrying an LED die 4 and a converter material 6 deposited on the LED die 4. The LED die 4 can include one or more light emitting components. FIG. 1B is a cross-sectional diagram of a portion of a conventional indium-gallium nitride LED 10. As shown in FIG. 1B, the LED die 4 includes a substrate 12, N-type gallium nitride (GaN) material 14, an indium gallium nitride (InGaN) material 16 (and/or GaN multiple quantum wells), and a P-type GaN material 18 on one another in series. Conventional substrates 12 are comprised of sapphire, silicone carbide, or silicon. The LED die 4 can further include a first contact 20 on the P-type GaN material 18 and a second contact 22 on the N-type GaN material 14. Referring to both FIGS. 1A and 1B, in operation, the InGaN material 16 of the LED die 4 emits a blue light that stimulates the converter material 6 to emit a light (e.g., a yellow light) at a desired frequency. The combination of the blue and yellow emissions appears white to human eyes if matched appropriately.
Although LEDs produce less heat than conventional lighting devices, one challenge of SSLDs in general is that some of the components are sensitive to heat and the LED die 4 or SSLE produces enough heat to increase the rate that such components deteriorate. The substrate 12 may have a relatively low thermal conductivity such that it traps the heat and raises the temperature of the converter material 6. The converter material 6 deteriorates relatively rapidly at higher temperatures, which causes the converter material 6 to emit light at a different frequency than the desired frequency. As a result, the combined emissions appear off-white and may reduce the color fidelity of electronic devices. A device that provides thermal cooling at the junction between LED die 4 and the substrate 12 would increase the reliability of white light production and maintain the desired color of light for longer periods. Additionally, thermal cooling at the junction would increase the efficiency and the life span of LEDs. Therefore, several improvements in managing the thermal cooling in LED packages, and more generally SSLDs, may be desirable.